APPLIED POPULATION ECOLOGY PDF
Request PDF on ResearchGate | On Oct 1, , Eric Rexstad and others published Applied Population Ecology: Principles and Computer Exercises Using . Akcakaya Et Al ()- Applied Population Ecology - Free ebook download as PDF File .pdf), Text File .txt) or read book online for free. ecología poblacional. Applied Population Ecology and the accompanying software, RAMAS® EcoLab , constitute an excellent quantitative introduction to the.
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Population ecology is the science that hwlps us understand why abundances and densities of a particular species vary in space and time. In the face of. Your use of this PDF, the BioOne Complete website, and all posted and associated content indicates Applied Population Ecology: Principles and Computer. This text is in PDF format and the accompanying RAMAS software is designed for Applied Population Ecology introduces junior- and senior-level.
The end-of-chapter exercises progress from introductory to more advanced.
Some undergraduates may find the most advanced exercises difficult because they require integration of concepts covered in previous chapters.
Thus, undergraduates may need more guidance on these exercises or should be encouraged to work on them in groups. In most chapters, it is desirable for students first to complete the easier exercises because they establish basic skills necessary to use the software for the more challenging exercises. The exercises are appropriate and adequately challenging for advanced undergraduates taking their 1st advanced ecology course and perhaps for beginning graduate students. However, instructors using the software in a graduate course may want to provide additional, more advanced exercises.
Although undergraduates will appreciate the step-by-step instructions that walk the user through each exercise, most graduate students will not like the extensive handholding. We challenge the authors to provide more advanced exercises marked as such appropriate for the graduate level in the next edition of the text and software.
This simple addition would provide a wider market for their product. There are 2 primary areas where the text diverges from more traditional textbooks on population ecology.
First, models are developed exclusively in discrete time with difference equations, and there is only brief mention of models developed in instantaneous time with differential equations.
We did not find this approach problematic, but instructors who wish to cover continuous population growth may want to supplement the text with lectures or readings. Second, the emphasis on the role and implications of variability and uncertainty in population dynamics and model building makes this text superior to more traditional population ecology textbooks.
We will explore this factor in the next chapter. However, this kind of variation is unimportant in large populations.
This implies that population density remains low enough for there to be no competition among members for limiting resources. These processes related to density-dependent effects are discussed in Chapter 3. Essentially, we assume that individuals are identical. In real populations, the probability of surviving, the number of surviving offspring produced, and the propensity to Applications immigrate or emigrate are not likely to be the same for different individuals in a population.
They may depend to some extent on the age, sex, size, health, social status or genetic properties of the individuals. However, it turns out that even if birth and death rates are, say, age-dependent, the mean rate per individual will remain constant if the proportions of the population in each age class remain constant over time see Chapter 4.
Thus, it is sufficient to assume that the proportion of individuals in these different categories such as age remains the same. This assumption will be violated by, for example genetic changes in the population, or by changes in the sex ratio the relative numbers of males and females , or by changes in the age structure the relative numbers of individual in different ages.
In Chapters 4 and 5, we will discuss models that track changes in the composition of a population. Within the population, the individuals are mixed.
The interaction with other populations of the same species is characterized by the rates of emigration as a constant proportion of the abundance per time step , and immigration as a constant number of individuals per time step.
This implies that the individuals killed by the additional mortality caused by control efforts would, in a sense, have been victims of mortality in any case, and were not important from the perspective of population growth. It is indeed possible that overcompensation may result from addition of mortality sources, when reductions in density and associated reduction in density dependent mortality actually exceed the increase in mortality caused by the added source of death i.
This circumstance can yield lower total mortality and greater population size after control efforts Washburn et al. Finally it is also possible that an additional source of mortality may be additive, when the added source of mortality has the intuitive effect of increasing observed total mortality Washburn et al.
Additive effects are desirable from a biological control perspective and are typically assumed in biological control efforts Washburn Because mortality sources that produce compensation or overcompensation are consequences of density dependent effects and because the result can be ineffective biological control i. Although intraspecific competition and density dependent mortality have received the most attention Southwood et al. Effects of small adult size, induced by food shortage, may also include reduced adult longevity Haramis Thus, density dependence among mosquito larvae is common, and this implies that any attempts to use biological control agents to impose mortality on mosquito larvae must consider whether the resulting mortality is likely to be compensating, overcompensating, or additive.
Such effects have been observed with conventional chemical larviciding e. Important questions that arise from considering this issue are: 1 Which habitats and mosquito species are least likely to suffer density dependent effects, and so potentially show additive effects of introduction of biological control agents?
Habitats and density dependence Service reviewed the literature on mortality affecting immature mosquitoes and concluded that overcrowding and density dependent mortality were often major factors affecting populations of container breeding mosquitoes, including those in both natural and human-made containers. In contrast, for ground water habitats such as ponds and marshes, Service concluded that density dependent mortality was less important. Fish posed similar questions, and assessed patterns of adult size variation and skewness as indices of competition and density dependent effects acting on growth and development of larvae.
He concluded that species in more ephemeral habitats tree holes, temporary pools had more variable, and more right skewed adult body size distributions, indicating a high level of intraspecific competition. In contrast, species inhabiting permanent habitats were less variable and not right skewed, suggesting little or no effect of intraspecific competition.
He suggested that these differences arise because of the relative rarity of predation in more ephemeral habitats.
Presumably predation in permanent ground water habitats keeps larval populations low resulting in most individuals attaining their maximum adult size.
This conclusion was also reached by Washburn Studies of individual mosquito species in ephemeral or container habitats indicate strong density dependent effects on mosquito populations e.
They concluded that in temporary wetlands, mosquito populations were always low and populations of non-mosquito competitors were uniformly high, suggesting strong interspecific competition in these largely predator-free habitats. Mosquito populations were likewise low in permanent wetlands, but in contrast to temporary wetlands, predator populations were always high. In drought years, predator populations crashed, and remained low into the following year.
During this year after a drought, mosquito populations increased by about an order of magnitude.
These results are consistent with the observations by Fish , and Washburn , implying that density dependent effects of competition are strongest in the most ephemeral habitats, and implicating predation as the process limiting mosquito density and possibly density dependence in more permanent habitats. They also provide an example of how following the dynamics of mosquito populations and their enemies could enhance the effectiveness of biological control.
Control efforts might target populations that have been released from predation pressure due to climatic effects on predators. Biological control in container and ephemeral habitats The prominence of density dependent mortality and growth affecting mosquito population dynamics in ephemeral or container habitats suggests that compensating or overcompensating mortality may result from introduction of novel predators or pathogens, limiting success of biological control.
In contrast, in more stable or larger habitats, introduction of pathogens and predators may be more likely to produce additive mortality and thus reduce production of adult mosquitoes.
Washburn et al. The absence of effects of this predator on production of O. Lounibos showed that pupation success of O. This study suggests overcompensation is the likely result of predation by C. In addition to these studies directly addressing patterns of predator-induced mortality, a number of studies of container-dwelling predators indicate that presence of predators, either native or introduced, reduce the numbers of prey mosquitoes in the system e.
These studies seem at odds with the inference described above that in container habitats, density dependent food limitation acting on larvae is prominent and that compensating or overcompensating effects of predation are likely. However, in a number of these studies predators have only been shown to affect abundances of larvae.
In order to evaluate whether compensation or overcompensation occur, data on production of adults or at least of pupae are necessary because density dependent mortality may occur among larvae late in development. Predatory larvae of the culicid genus Toxorhynchites have been shown repeatedly to reduce production of adult or pupal container-dwelling mosquitoes e. Thus, this predator is capable of imposing sufficient mortality on populations of larvae and pupae to render the effect of that mortality additive, despite density dependence in container dwelling prey.
Most failures have been ascribed to failure of Toxorhynchites to oviposit in the target habitat i. This latter effect is an example of how population dynamics of an enemy are related to probability of successful control, which is discussed below.
Investigations of predation by cyclopoid copepods have more commonly examined effects of predators on abundances of larvae e. Like Corethrella and Anopheles barberi see above , copepods prey primarily on small larvae, and because density dependent effects may impact larger, older larvae, it seems likely that compensation or overcompensation could result from copepod predation in at least some circumstances, and this would be an interesting avenue for further research.
Thus, it seems likely that biological control of container mosquitoes will be difficult because control attempts may be foiled by compensating or overcompensating mortality. There is both direct Lounibos , Washburn et al. Merely knowing that the target of a control program is from a habitat e. Quantitative data on density dependent mortality when? Relatively few attempts have been made at biological control of mosquitoes in ephemeral ground water habitats, and no one has explicitly considered whether mortality is additive, compensating, or overcompensating.
Introductions of tadpole shrimp Triops sp to temporary pools have produced effects on mosquito populations that suggest additive mortality Fry et al. Stav et al.
The effects of this predator suggest additive mortality. Further, Stav et al. These results for experimental ephemeral ground water habitats are consistent with additive mortality imposed by a generalist predator, and thus suggest that biological control by predators would be successful in this habitat.
Introduction of Gambusia to ephemeral habitats has also produced successful mosquito control reviewed by Murdoch et al.
Thus, for ephemeral ground water habitats, limited data suggest that additive mortality may be common, and prospects for biological control may be better than for container habitats. Biological control in permanent ground water habitats In these habitats, consideration of density dependent effects on mosquito population dynamics leads to the expectation that additive mortality should be prevalent, and biological control efforts should be more likely to succeed. The most commonly employed methods of biological control for mosquitoes in permanent ponds are releases of mosquitofish Gambusia and a few other fish species, and application of Bacillus thuringiensis var.
Classical biological control of mosquitoes with fish in small permanent ponds, ditches, and rice paddies is generally regarded as successful, in the sense that mosquito populations are reduced Murdoch et al , although there are many instances in which introduced Gambusia have become threats to native fish, amphibians, and invertebrates e.
Despite these concerns, a number of state and local agencies in the U. However, data documenting the effectiveness of Gambusia in reducing pupation or adult production are scarce Bence There are instances in which mosquitofish fail to produce reductions of numbers of adults Blaustein and in some cases introduction of mosquitofish has resulted in increased abundances of mosquitoes reviewed by Bence In reviewing these cases, Bence suggested that when mosquitofish cause increases in mosquito abundance, that effect arises because of indirect effects on mosquito populations mediated via predation by mosquitofish on other predators of mosquitoes.
If this hypothesis is correct, these failures have not arisen because of compensation or overcompensation in the mortality of the target mosquitoes, but rather through community wide impacts of the biological control agent.
Such effects seem particularly likely and worrying for generalist predators see below. These kinds of potential effects suggest that in addition to reviewing the implications of population dynamics for biological control of mosquitoes i. Bti and Bs have been used effectively as biopesticides, producing reductions of mosquito populations e.
Reintroduction of the pathogen or toxin is typical.
No studies have specifically investigated whether these pathogens cause additive, compensating, or overcompensating mortality in these habitats, hence we cannot evaluate the role of density dependent mortality in these systems. Because larviciding can result in compensatory mortality of mosquitoes, at least under laboratory conditions Agudelo-Silva and Spielman , it is at least possible that larviciding with Bti or Bs can also produce this effect.
For permanent ground water habitats, the data suggest that additive mortality is common and thus successful biological control may be likely in these habitats.
Biological control seems a better prospect in the latter group. When during the life cycle does density dependence occur?
Service argued that added mortality imposed by a control agent should act after density dependence has taken its toll on a target mosquito population. He suggested that enemies that attack late larval or pupal stages would therefore be most effective as biological control agents and that killing eggs or early stage larvae would be less effective Service Service based this suggestion on the expected effects of density dependent death and the potential for compensating mortality from control efforts, however, the conclusion that targeting late larvae and pupae is most effective also derives from consideration of reproductive value for individuals, which is maximal just prior to the transition to adulthood, rendering control of these stages more effective for reducing population size Lounibos et al.
These considerations would suggest that predators such as Toxorhynchites, Gambusia, Notonecta, and nematode parasitoids which kill late instar larvae and pupae are likely more desirable control agents than are copepods and other small predators like Corethrella and A.Preface Practical ecological problems such as preservation of threatened species, design of nature reserves, planned harvest of game animals, management of fisheries, and evaluation of human impacts on natural systems are addressed with quantitative tools, such as models.
Population censuses of Muskox on Nunivak Island between and The mean predicted by the model including demographic stochasticity Figure 2.
Calculate the fecundity and the annual growth rate for years , , and , and enter them in Table 1. We know the population sizes in all years between and Biologists have recognized for many centuries that limits must exist for most species, either in the form of extremes of physical variables, or in the form of competitors and predators.
Metapopulation structure evolves from year to year, where some patches are sinks, such as dry years, and become sources when conditions are more favorable. However, this kind of variation is unimportant in large populations.
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